Chemistry Term 1

• Mass spectrometry is an analytical technique used to determine the mass and relative abundance of atoms and molecules in a sample.
• what is density?

  mass per volume
• Distinguish between emission and absorption spectra

  Emission Spectrum: light given off when an atom jumps

  Absorption Spectrum: electrons absorbing so they can jump out
• What do the Black lines in the absolution spectra show?

  The wavelengths that are missing since that energy has been absorbed by elements
• Flame Emission Spectroscopy is a technique that measures light coming from a light source and separates it into specific wavelengths
• The overall color of a light source is often a mixture of wavelengths, like barcodes or fingerprints
• Each line on a spectra represents a specific electron jump in the visible wavelengths range
• We can only see the jumps in the visible wavelengths range
• The spectral lines are like barcodes or fingerprints
• The Prism in Flame Emission Spectroscopy separates the light into specific wavelengths
• The Detector in Flame Emission Spectroscopy detects the separated wavelengths
• The Green Arrows in the spectroscopy represent specific electron jumps
• The Red Arrows in the spectroscopy represent the Hyman Series
• The Yellow Arrows in the spectroscopy represent the Paschen Series
• The single electron that Hydrogen has can make jumps in different series:

  • Balmer Series (visible): The electron returns to n=2 (second energy level)
  • Lyman Series (ultraviolet): The electron returns to energy level 1 or ground level
  • Paschen Series (infrared): The electron returns to n=3
• Flame tests and Atomic Absorption Spectroscopy (AAS) are analytical methods used to identify elements
• These techniques rely on electron transfer between atomic energy levels and line spectra
• When elements are burnt, they produce specific colors, which can be used for identification
• Spectroscopy uses the wavelength of light to provide information about frequencies and properties of materials
• Quantum Theory explains that atoms absorb light and emit electromagnetic radiation at specific frequencies
• Different parts of the atom are affected by different electromagnetic radiation
• All elements have specific absorption techniques that rely on energy levels and are shown when heated
• When electrons in energy level shells absorb energy, they can change color when heated
• If the wavelength of light absorbed by electrons in an outer shell is in the visible region, a specific amount of energy is given off as light of a specific color
• For example, sodium emits orange light at 620 nm when heated
• Some metals change color when heated due to electron energy level transitions
• When electrons absorb energy, they are not stable and will give off the energy and return to their normal place or ground state
• Relative atomic mass is the weighted average mass of an element based on the abundance of its isotopes
• Mass spectrometry involves the appropriate mathematical representation, including calculating the element and percentage abundance of isotopes
• Each peak in a mass spectrum represents an isotope of the element
• The height of the peak indicates the relative abundance of that isotope
• The position on the x-axis in a mass spectrum indicates the mass of the ion
• Isotopes are different forms of an element with the same number of protons but different numbers of neutrons
• The relative atomic mass of an element is the ratio of the average mass per atom of the naturally occurring isotopes of the element to 1/12 the mass of a carbon-12 atom
• For example, for Magnesium:

  • 79% of 24Mg
  • 10% of 25Mg
  • 11% of 26Mg

  The calculation would be: (0.79 x 23.985) + (0.1 x 24.986) + (0.11 x 25.983) = 24.31
• The values obtained from the isotopic abundances lead to the relative atomic mass seen on the periodic table